1) Field of the Invention
The invention relates to polymer compositions in the form of their aqueous dispersions or powders redispersible in water, processes for their preparation and their use for flexibilizing building materials, in particular sealing slurries.
2) Background Art
It is known that the extensibility of building materials can be improved by adding aqueous dispersions of thermoplastics. For example, flexible sealing slurries as used for sealing concrete consist of sand, cement, water and a thermoplastic polymer dispersed therein. The procedure adopted to date was to attempt to improve resilience by changing the polymer composition of the thermoplastics. WO-A 97/44289 teaches the use of copolymers based on vinyl acetate/ethylene copolymers which have a proportion of long-chain, optionally branched vinyl esters for improving the flexibilization. EP-A 857772 proposes, for improving the resilience of cement-free joint sealing compounds, modifying them with a mixture of thermoplastics and alkylalkoxysilanes. EP-A 590660 teaches that the water repellency of cement-free sealing compounds can be improved by adding thermoplastic polymers and branched organopolysiloxanes.
It was the object of the invention to develop a polymer composition by means of which, independently of the composition of the thermoplastic polymer, effective flexibilization of building materials, in particular of cement-containing building materials, is obtained.
The invention relates to a polymer composition for flexibilizing building materials, in the form of their aqueous dispersion or of powder redispersible in water, containing:
a) at least one water-insoluble, film-forming polymer of one or more ethylenically unsaturated monomers capable of free radical polymerization,
b) at least one compound from the group consisting of the water-soluble polymers of one or more ethylenically unsaturated monomers capable of free radical polymerization, and the ionic and nonionic emulsifiers, and
c) a mixture of at least two organosilicon compounds, at least one of which is an amino-functional organosilicon compound present in salt form.